Today, a mobile device must comply with recognized mobile radio standards and protocols in its communications with a network. When a mobile device computes a position estimate, it first determines what mobile-based position methods are supported by the network. For example, a mobile device may monitor overhead information broadcast by the network. Within this overhead information, the network may announce what positioning method or methods it supports. Alternatively, a mobile device may receive information on which position methods a network supports in a point to point manner from an entity within the network (e.g. a location server). Alternatively, a mobile device may request assistance data tailored for a particular positioning method. Assistance data tailored for a particular method shortens the assistance data by leaving out extraneous types of data not used by that positioning method. If the network and mobile device both support a common mobile-based positioning method using the requested assistance data, the mobile device may request and receive assistance data for that particular common positioning method. Once a mobile device receives the assistance data, the mobile devices uses it to compute a position estimate.
Different positioning methods require different sets of information. Therefore, each type of assistance data message includes a different set of information. That is, a network tailors an assistance data message to contain the required set of information for a particular positioning method. As a result, the network transmits just the information needed for a selected positioning method. The network does not transmit extraneous and unnecessary information not needed and not used by the mobile device for the selected positioning method.
If a mobile device wishes to perform an alternate positioning method, which uses a different set of assistance data, the mobile device may learn from the network that the alternate positioning method is not supported by the network. Alternatively, the mobile device may be aware that a position method is not supported by the network. For example, the position method may not be defined by a standard that the network follows (e.g., a wireless network implementing a standard from 3GPP, 3GPP2 or OMA). In this case, the mobile device will not invoke the alternate positioning method and instead either falls back to some common positioning method or perform no positioning. For example, the mobile device might not support a position estimate based on the first positioning method but supports only a second positioning method. If the network does not support the second positioning method, the mobile device and network will be incompatible and incapable of supporting any mobile-based positioning method.
In other cases, a mobile device is able to compute a position estimate based on the first positioning method but selects to compute a position estimate based on the second positioning method. The second positioning method may have some benefit over the first positioning method, such as being less computationally intensive or requiring less power, which extends battery life of the mobile device. Alternatively, the second positioning method may be proprietary to a particular vendor or non-conforming to an industry standard or protocol. Disadvantageously, if the network does not also support the second positioning method, the mobile device will not use the second positioning method.